This proposal deals with studies on the post-transcriptional regulation of protein synthesis in the fungus Mucor racemosus. We have shown that a group of proteins, synthesized specifically during morphogenesis, is not regulated at the level of transcription, since the mRNA for these proteins can be extracted and translated in an in vitro wheat-germ system. In addition, properties of the regulation of ornithine decarboxylase (ODC) point to regulation at both the post-transcriptional and post-translational level. We will study the elements of the controlling factor(s) which allow translation of pre-existing mRNA. In addition, we will develop an in vitro system for the synthesis of ODC by first cloning the gene for the enzyme on an E. coli plasmid.